1. Field of the Invention
The present invention relates to a power supply system mounted on a vehicle.
2. Description of the Related Art
There is conventionally known a fuel cell power supply system mounted on a vehicle, which system includes a fuel cell, a secondary battery, a voltage boosting means having one end connected to the fuel cell and another end connected to the secondary battery and for boosting a voltage on the one end for supply to the other end, and a plurality of electric motors each provided on either end of the voltage boosting means (see Japanese Patent Application Laid-Open No. 2006-288129). In this power supply system, load distribution to the plurality of electric motors is controlled in accordance with the operating state of the fuel cell and the charge level of the secondary battery.
For charging the secondary battery, part of the electric power output from the fuel cell is supplied via the voltage boosting means to the secondary battery, and regenerative energy from the electric motors is also supplied to the secondary battery.
The fuel cell uses hydrogen as its fuel. There are only a limited number of stations for charging the hydrogen. Thus, it is desired to use the output power from the fuel cell for running the vehicle as much as possible, to reduce the consumed amount of the hydrogen.
Furthermore, the electric power supply from the fuel cell to the secondary battery may be reduced by charging the secondary battery in advance from an external power source. This however may require a dedicated charging facility. Further, using a general commercial power supply for charging will cost much time as well as much money.